CN102083126A - Relay node switching for different transceivers used for different repeated links - Google Patents

Abstract

The invention relates to relay node switching for different transceivers used for different repeated links, describing a relay node of a radio telecommunication network. The relay node comprises a first transceiver and a second transceiver, wherein the first transceiver is suitable for being operated in a first operation mode, wherein a return data communication volume is transmitted through a first relay repeated link extending between the relay node and a first base, and the first base refers to the source access point of the relay node; and the second transceiver is suitable for being operated in a second operation mode, wherein, in the preparation of switching the relay node from the first base to the second base referring to the target access point of the relay node, the access program is performed through a second repeated link extending between the relay node and the second base. The invention further describes a preparation method of switching the corresponding relay node from the first base to the second base.

Description

Relay Node Switching Using Different Transceivers for Different Relay Links

technical field

The present invention relates generally to the technical field of relay-enhanced wireless telecommunication networks. In particular, the invention relates to a relay node capable of handover from a first (source) base station to a second (target) base station of a cellular telecommunication network. Furthermore, the invention relates to a method for preparing a handover of a relay node from a first base station to a second base station.

Background technique

For Long Term Evolution (LTE) telecommunication networks, and especially for LTE-Advanced telecommunication networks, the use of relay nodes (RNs) is seen as a tool to improve e.g. (a) spatial coverage at high data rates, ( b) group mobility of user equipment (UE), (c) temporary network deployment, (d) data throughput on cell edge and/or (e) coverage in new areas of the telecommunication network.

A relay node is wirelessly connected to a radio access network (RAN) through a base station (BS). This base station is usually called a donor base station and the corresponding cell of the telecommunication network defined by the donor base station is called a donor cell. Depending on the relay strategy, the RN may (a) be part of the donor cell or (b) control its own cell.

In case the RN controls its own cell, the RN controls one or several cells. Further, a unique physical layer cell identity is provided in each cell controlled by the RN. A user equipment typically sees a relay node as a normal BS, which is called an evolved NodeB (eNB) in LTE.

In the case of a two-hop relay deployment, where the UE is connected to the donor base station via exactly one RN, the wireless link between the relay node and the donor base station is called a relay link and is overlaid between the relay node and the relay node A wireless link between user equipments in range is called an access link. For a relay node controlling its own cell, the relay node can be regarded as a micro base station with self-backhaul function. Relay links are used to transport backhaul traffic to and/or from the radio access network. The access link is used to provide coverage for the user equipment under the cell. Compared with large-area base stations, the spatial coverage of typical relay nodes is typically smaller, the number of served user equipment is smaller, the wireless channel condition in the access link is better, and the peak data achieved by each user equipment Throughput is higher.

Since the coverage area of a relay node is small, more relay nodes will have to be deployed in a large area. Thus, relay nodes with self-organizing capabilities will help reduce installation and operation costs. Such a relay node is a hybrid device with access function and self-backhaul function. Therefore, the ad hoc nature of relay nodes has two aspects: (a) ad hoc organization of relay links and (b) ad hoc organization of access links.

Self-organization of the relay link means that the relay node automatically selects the donor base station. In case the current relay link is bad, the relay node can reselect a new donor base station which allows better wireless channel conditions. This reselection of a new donor base station is called relay node handover (HO). Self-organization of access links means that the coverage area and access capabilities of relay nodes can be changed according to current needs and provide optimized performance.

Known relay nodes are equipped with a radio transceiver for the relay link extending between the relay node and the donor base station. Alternatively, the radio transceiver used for the relay link may additionally be shared with the access link. As a result, a relay node can only establish a relay link with one donor base station at the same time. This mainly raises two questions:

Problem 1: In the case where the relay node switches from the old source (donor) base station to the new target (donor) base station before it can start detaching from the source base station, the relay node must not Necessary access procedures with the target base station are not performed. During the handover period, the transmission of backhaul traffic in the relay link is suspended, and the source base station needs to buffer this backhaul traffic and transmit the corresponding data packets to the target using the so-called X2 interface extending between the source and target base stations base station. The buffered backhaul traffic will be retransmitted by the target base station to the relay node after the handover is successfully completed. However, such known relay node switching procedure has the disadvantage that it causes additional long delays for backhaul traffic and affects the end-to-end quality of service (QoS) of wireless data traffic, especially of real-time services.

Question 2: To support self-organization of relay links, wireless channel quality measurements usually play a key role. Through such measurements, the relay node can collect important information, such as channel state signal strength and/or interference strength between the relay node and donor base stations around the relay node. When the relay node performs such measurements for different frequencies in different relay links, the donor base station will have to suspend its backhaul transmission, which will reduce the data throughput capacity. In addition, if both the donor base station and the relay node are located at fixed locations, the relay node may employ narrow-beam directional antennas in the relay link in order to increase signal strength and reduce interference. This means that the relay node needs to steer its antenna direction when it measures the radio channel quality of a radio link extending between the relay node and a candidate target base station located in other directions. This may increase the measurement time even if the source base station and the candidate target base station operate on the same carrier frequency.

The two problems mentioned above will seriously affect the data throughput capability of the relay link. Unlike the UTRAN to user equipment (Ue) interface, which is defined between the user equipment and the serving base station, and which carries traffic for only a single user equipment, a relay link will typically carry Backhaul traffic for all user equipment connected to the relay node. Therefore, instability in the relay link will affect the performance of all these user equipments. Therefore, the relay link should be more reliable than the access link, which accordingly carries the data traffic of only a single user equipment.

This requires improving the stability of the relay link extending within the telecommunications between the relay node and the different possible donor base stations.

Contents of the invention

This need is met by the subject-matter as stated in the independent claims. Preferred embodiments of the invention are described by the dependent claims.

According to a first aspect of the invention there is provided a relay node for a radio telecommunication network. A relay node is provided comprising (a) a first transceiver adapted to operate in a first mode of operation wherein backhaul data traffic is via a first relay link extending between the relay node and a first base station is conveyed that the first base station represents the source access point of the relay node: (b) a second transceiver adapted to operate in a second mode of operation wherein the relay node is handed over from the first base station to represent In preparation of the second base station of the target access point of the relay node, an access procedure is performed via a second relay link extending between the relay node and the second base station.

The described relay node (RN) is built on the idea that if the relay node has a minimum of two independent transceivers - both of which are allocated for communication between the relay node and at least a first and a second base station ( For the relay link extending between BSs), the relay node handover (HO) can be done in a very efficient manner. In a relay node handover procedure, the first base station is the source base station and the second base station is the (candidate) target base station. Since the handover procedure and the transfer of backhaul data traffic can be performed simultaneously, high efficiencies especially with regard to data throughput can be achieved. As a result, there are shorter time gaps during which backhaul data traffic has to be suspended compared to known relay node handover procedures where only one transceiver is configured for a different relay link. This leads to the advantageous result that a smaller amount of data will be buffered on the first (source) base station during handover preparation.

In general, the described relay nodes are provided with two different transceivers for relay link transmissions. The first transceiver may be contemplated as an active transceiver for connecting the relay node with the first (source) base station for backhaul data traffic transmission. The second transceiver may be expected as a backup transceiver since it may only be used for handover preparation when a relay node handover from the first (source) base station to the second (target) base station is considered. While the standby (second) transceiver performs a handover access procedure to the target base station, at the same time, the active (first) transceiver still maintains backhaul data traffic transmission with the source base station via the active first relay link.

In the described relay node, multiple transceivers may be used only to (a) reduce handover and measurement time (for handover preparation) and/or (b) increase reliability of the relay link. During only a short moment, a relay node may keep more than one relay link in Radio Resource Control (RRC) connected state. However, this will typically not affect the network architecture too much.

According to an embodiment of the invention, the first transceiver is adapted to operate with a first carrier frequency and the second transceiver is adapted to operate with a second carrier frequency. Thus, the first carrier frequency is different from the second carrier frequency. This may provide the advantage that an efficient relay node handover procedure can also be performed if the first source base station operates on a different carrier frequency than the second target base station.

According to a further embodiment of the invention, the first directional antenna pattern is associated with the first transceiver and the second directional antenna pattern is associated with the second transceiver. Thus, the first directional antenna pattern is spatially different from the second directional antenna pattern. This may provide the advantage that by deploying beamforming techniques, the radiation emitted by the first transceiver can be spatially positioned towards the first base station and/or the radiation emitted by the second transceiver can be spatially positioned towards the second base station. This also applies to the reception case, whereby the sensitivity of the first transceiver to radiation from the location where the first base station is located can be increased. Correspondingly, the sensitivity of the second transceiver to radiation from the location where the second base station is located can be increased.

In other words, by applying beamforming techniques, the second base station can be positioned in a direction not directly pointed by the antenna direction of the first active transceiver.

In this respect it is mentioned that beamforming is a known signal processing technique which can be used in antenna arrays for directional signal transmission or reception. Thus, spatial selectivity is achieved by using adaptive, switched or fixed receive/transmit beam patterns. The improvement compared to undirected reception/transmission is called reception/transmission gain.

According to a further embodiment of the invention, the relay node further comprises a common antenna, which is assigned to the first transceiver and the second transceiver. This may provide the advantage that the relay node can be implemented using only one antenna, which is used by both the first and the second transceiver.

It is mentioned here that the common antenna may contain one or more antenna elements. The beamforming described above can be achieved when using different antenna elements which are fed the same radio signal, but with different appropriate phase shifts. Again, this also applies to reception situations in which the sensitivity of the received radio signal is spatially inhomogeneous.

According to a further embodiment of the invention, the relay node further comprises (a) a first antenna assigned to the first transceiver and (b) a second antenna assigned to the second transceiver. Therefore, the first antenna is distinct from the second antenna. This can be particularly advantageous if the first and second transceivers operate with different spatial direction antenna patterns.

According to a further embodiment of the invention, the second transceiver is further adapted to operate in a further first mode of operation, wherein backhaul data traffic is transmitted via a second relay link extending between the relay node and the second base station Passing, the second base station represents a further source access point for the relay node after handover from the first base station to the second base station has been completed.

This may mean that the second initial backup transceiver may represent the active transceiver after the second backup transceiver has switched in to the second (target) base station and the handover has been successfully completed. This may provide the advantage that the connection between the second transceiver and the second base station need not be released or terminated after a handover has been successfully completed.

Generally, after the handover is complete, the old standby transceiver will become the new active transceiver and will exchange backhaul data traffic with the target base station in the new trunk link.

According to a further embodiment of the invention, the first transceiver is further adapted to operate in a further second mode of operation, wherein at the relay node from the second base station to a third base station representing a further target access point of the relay node In preparation for a further handover of , a further access procedure is performed via a third relay link extending between the relay node and the third base station.

This may mean that after the second backup transceiver successfully accesses the second (target) base station, the active transceiver will leave the original source base station and become the new backup transceiver for preparing the relay node for further handover.

In this respect it is mentioned that the third base station may be any base station in the telecommunication network in addition to the second base station. In particular, (a) the third base station may be different from the first and second base stations or (b) the third base station may be the first base station. The latter means that with respect to the first handover, the second handover has the opposite direction, ie the relay node is handed over from the second base station to the first base station.

According to a further aspect of the present invention there is provided a method for preparing a handover of a relay node from a first base station to a second base station of a cellular telecommunication network, wherein the relay node comprises a first transceiver and a second transceiver. A method is provided comprising: (a) operating a first transceiver in a first mode of operation, wherein backhaul data traffic is communicated via a first relay link extending between a relay node and a first base station, the The first base station represents a source access point for the relay node, and (b) operates the second transceiver in a second mode of operation, wherein the relay node switches from the first base station to a target access point representing the relay node In preparation for the second base station of the node, an access procedure is performed via a second relay link extending between the relay node and the second base station.

The described method is likewise based on the idea that if two independent transceivers are involved - both of which are allocated for a relay link extending between a relay node and at least a first and a second base station BS, the relay Node Handover (HO) can be done in a very efficient manner. In a relay node handover procedure, the first base station is the source base station and the second base station is the (candidate) target base station. High efficiencies in particular with regard to data throughput can be achieved, since handover preparation and transfer of backhaul data traffic can be performed simultaneously.

It is pointed out here that the described method can also be applied in a corresponding manner in the handover preparation of a user equipment from a first radio access point to a second radio access point, wherein the user equipment contains two radio transceivers and/or a dual radio transceiver. Thus, the first radio access point may be a first base station or a first relay node. Correspondingly, the second radio access point may be a second base station or a second relay node. Thus, the same concept can be applied with respect to the interplay between active and standby transceivers as described above for the relay node.

According to an embodiment of the invention, the access procedure performed via the second relay link comprises performing a measurement procedure, which is related to a handover decision of the relay node from the first base station to the second base station.

The relay node may in particular be configured by the first base station to perform suitable measurement procedures. Receiving a corresponding configuration message, the relay node is able to start a second radio transceiver to measure radio cells operating on different frequencies parallel to the transmissions of the respective first base station of the source or serving cell. This may provide the advantage that measurement intervals during inter-frequency measurements can be avoided entirely or can be at least significantly reduced.

According to a further embodiment of the present invention, the method further comprises informing the first base station of the fact that the relay node is configured with the first transceiver and the second transceiver. This may provide the advantage that the base station may employ the following handover procedure to yield the fact that the efficient handover procedure described above can be performed. This is particularly advantageous if the telecommunications network comprises relay nodes of different types at least one of which is equipped with two transceivers as described above. Thus, depending on the capabilities of the respective relay nodes, base stations can prepare for conventional relay node handover or the improved relay node handover procedure described above benefiting from having two transceivers available for different relay links .

Preferably, the base station is notified directly by the relay node. This can for example be achieved together with and/or within the measurement report which is transmitted from the relay node to the first base station and wherein the relay node reports to the first base station, in particular between the relay node and the first base station The quality of the radio channel extended between.

Alternatively, the capability of the relay node indicating the presence of two transceivers may be reported from the relay node to the first base station via a relay node capability transfer message, which may be requested by the first base station.

According to a further embodiment of the invention, the method further comprises informing the relay node that the first base station continues to serve the relay node via the first transceiver during the execution of the access procedure with the second transceiver. This may provide the advantage that the relay node will be notified of the fact that the first base station is aware of the improved capabilities of the relay node. Therefore, reliable handover of the relay node from the first base station to the second base station can be achieved. In other words, with corresponding notification signaling, the relay node is notified (eg by the first base station) that the relay node should keep its first transceiver active.

In response to this information being provided to the relay node, the relay node can continue the data packet transmission with the first base station. At the same time, the second or backup transceiver can perform synchronization to the second (target) base station.

According to a further embodiment of the present invention, the method further comprises (a) handing over the relay node from the first base station to the second base station, (b) transmitting a handover complete message from the second base station to the first base station indicating that the handover is complete , and (c) forwarding data from the first base station to the second base station, said data having been addressed to the relay node 140,240 and which has been buffered at the first base station 110,210. This may mean that the handover complete message may act as a trigger for starting forwarding of buffered data from the respective first source base station to the respective second target base station.

According to a further embodiment of the invention, the method further comprises deactivating at least the first transceiver associated with the first relay link extending between the relay node and the first base station. This may provide the advantage that the operation of the first transceiver can be curtailed, at least in part, if after a successful handover the service of the first trunk link will not be required. Therefore, the energy consumption of the relay node can be effectively reduced.

In this respect it is mentioned that at the relay node a predetermined time interval may be defined after a corresponding message indicating completion of the RRC connection reconfiguration has been sent to the second base station. If no data packets are delivered to and/or from the first base station by the previous first transceiver, or a predetermined time interval expires, the first transceiver may be switched off or the operation of the first receiver may at least be curtailed.

According to a still further aspect of the present invention there is provided a computer readable medium having stored thereon a computer program for preparing handover of a relay node from a first base station to a second base station of a cellular telecommunication network. The computer program is adapted, when executed by a data processor, to control or perform the handover preparation method described above.

The computer readable medium can be read by a computer or a processor. A computer readable medium can be, for example but not limited to, an electronic, magnetic, optical, infrared or semiconductor system, device or transmission medium. The computer readable medium may contain at least one of the following media: computer distribution medium, program storage medium, recording medium, computer readable memory, random access memory, erasable programmable read only memory, computer readable software distribution package, computer readable signal, computer readable telecommunications signal, computer readable printing device, computer readable compressed software package.

According to a further aspect of the invention, a program element is provided for preparing a handover of a relay node from a first base station to a second base station of the cellular telecommunication network. The program element, when executed by the data processor, is used to control or execute the handover preparation method described above.

Program elements can be implemented as computer-readable instruction codes in any suitable programming language such as JAVA, C++, and can be stored on computer-readable media (removable hard disk, volatile or non-volatile memory, embedded memory/ processor, etc.). Instruction codes operate to program a computer or any other programmable device to perform intended functions. Program elements are available from a network, such as the World Wide Web, from which they can be downloaded.

The present invention can be realized by software corresponding to a computer program. However, the present invention can also be realized by means of hardware corresponding to one or more specific electronic circuits. Furthermore, the present invention is also implemented in a hybrid form, for example, in a combination of software modules and hardware modules.

It is noted that embodiments of the invention have been described with reference to different subject matter. In particular, some embodiments are described with reference to apparatus type claims whereas other embodiments are described with reference to method type claims. However, a person skilled in the art will appreciate from the above as well as the following description that unless otherwise informed, apart from any combination of features pertaining to one type of subject matter, between features of different subject matter, in particular features of product type claims and method types Any combination between the features of the claims is considered to be disclosed in the present invention.

The aspects defined above and further aspects of the invention are apparent from and are explained with reference to the examples of embodiment described hereinafter. The present invention will be described in detail hereinafter with reference to examples of embodiment but the present invention is not limited thereto.

Description of drawings

Figure 1 shows a telecommunications network in which a first radio transceiver of a relay node is used to transmit and receive backhaul data with a first base station and at the same time a second radio transceiver of the relay node is used to prepare the relay node from the first base station A base station is handed over to a second base station.

Figure 2 shows a signaling diagram according to the invention and a corresponding handover-related measurement procedure for enabling the multi-transceiver feature in a relay node handover.

Figures 3a to 3d illustrate relay node switching situations benefiting from two transceivers for different relay links.

Detailed ways

The illustrations in the figures are exemplary.

Figure 1 shows a telecommunications network 100 that includes a two-hop relay deployment. Wherein, a relay node (RN) 140 is connected to a first base station (BS) 110 through a first relay link 111 . The relay node 140 currently serves three user equipments, which are located in the relay cell 141 . A first user equipment (UE) 150 is connected to the relay node 140 through a first access link 151, a second user equipment 160 is connected to the relay node 140 through a second access link 161 and a third user equipment 170 is connected to the relay node through a third access link. The incoming link 171 connects the relay node 140 .

The relay node 140 includes two radio transceivers, a first radio transceiver 142 and a second radio transceiver 144 . Further, according to the embodiment described here, the relay node 140 comprises two antennas, a first antenna 143 and a second antenna 145 . The first antenna 142 is assigned to the first radio transceiver 142 and the second antenna 145 is assigned to the second radio transceiver 144 . However, it is mentioned here that the relay node 140 can equally be configured with only one antenna or with more than two antennas. Further, the relay node 140 may be configured with more than two radio transceivers.

In the operational state illustrated in FIG. 1 , the first radio transceiver 142 is active and maintains all backhaul data traffic that is transmitted over the first trunk link 111 (in the uplink (UL) direction and/or in the downlink (DL) direction). The second radio transceiver 144 is a backup transceiver that may be switched off during most of the relay node 140's operating time.

However, for example when the relay node 140 recognizes that the channel quality of the first relay link 111 has deteriorated and/or the quality of the second relay link 121 extending between the relay node 140 and the second base station 120 is better than the first When the channel quality of the relay link 111 is reached, the backup transceiver 144 will become active and start the access procedure to the second base station 120 . This access procedure can be considered as part of the handover preparation of the relay node 140 from the first base station 110 to the second base station 120 . Of course, the same applies to the possible handover of the relay node 140 from the first base station 110 to the third base station 130 , and the third base station 130 may be connected to the relay node 140 through the third relay link 131 .

It is mentioned here that the described access procedure can be performed by the second radio transceiver 144 during time intervals when the first radio transceiver 142 is still busy handling the usual backhaul data traffic via the first trunk link 111 . Consequently, in the event of a relay node handover, data traffic to and/or from a different user equipment 150, 160, 170 has to be suspended for only a short period of time. As a result, the efficiency of the telecommunications network 100, and in particular the efficiency of the trunk links 111 and 121, with respect to data throughput capability, can be greatly enhanced by using a relay node 140 containing 111 and 121 are two independent radio transceivers 142 and 144 .

When a relay node 140 performs a handover from a first (source) base station 110 to a second (target) base station 120, when the target base station 120 uses a different frequency for its relay link transmissions and/or the target base station 120 is located at the active transceiver 142 In the case where the antenna 143 is not directly pointing in a direction, the backup transceiver 144 will perform an access procedure to the target base station 120, while the active transceiver 142 still maintains backhaul traffic transmission with the source base station 110 via the relay link 111. After the backup transceiver 144 successfully accesses the target base station 120, the active transceiver 142 will leave the source base station 110 and become the new backup transceiver. Generally, the old standby transceiver will become the new active transceiver and exchange backhaul traffic with the target base station over the new trunk link.

Figure 2 shows a signaling diagram according to the invention and a corresponding handover (HO) related measurement procedure for enabling the multi-transceiver feature in a relay node (RN) handover. The signaling diagram is illustrated in a so-called transaction flow diagram, in which the following network elements are involved: relay node 240 , first source base station 210 , second target base station 220 , mobility management entity (MME) 280 and serving gateway 282 .

The base stations 210, 220 may be, for example, evolved Node Bs in E-UTRAN. The base stations 210, 220 are able to communicate with other network elements such as other base stations or further relay nodes via wireless interfaces or via wired interfaces. The communication connection between different base stations is called the X2 interface in the E-UTRAN specification. Communication between different base stations can also take place via the S1 interface, which connects both base stations to the Serving Gateway and thus is not directly connected to each other.

In the taxonomy used in Figure 2, signal diagramming is subdivided into three stages. During the first phase 291 , the relay node 240 is a radio resource control (RRC) connected with the first base station 210 . During the second phase 292, the relay node 240 is connected to the RRC of the first base station 210 and to the RRC of the second base station 220 using an idle connection. During the third phase 293 the relay node 240 is RRC connected to the second base station 220 .

In a cellular telecommunication network, user equipment, not depicted in Figure 2, may be mobile terminals, which move through space. Moving terminals can introduce additional demands on the telecommunications network. Connections can be established on demand and resources can be released when they are no longer needed. Since a user equipment may be transferred to other cells due to its movement, serving network elements (base stations and, if applicable, relay nodes), may exchange information about the movement of the corresponding user equipment. The Mobility Management Entity (MME) 280 together with the Radio Resource Control (RRC) layer handles this exchange of information between the involved network elements. The mobility management entity 280 may maintain, for example, resource preparation on the target base station 220, allocation of user equipment to new radio resources, non-access signaling, tracking area list management, roaming, authentication and/or release resources. In other words, the mobility management entity 280 acts as an anchor point for mobile user equipment connections. Further, the base stations 210 , 220 may be logically connected to the mobility management entity 280 . The interface between the base stations 210, 220 and the mobility management entity 280 is called the S1 interface in the E-UTRAN specification. The Mobility Management Entity 280 is part of the Evolved Packet Core (EPC) in Long Term Evolution (LTE).

Serving gateway 282 may be included in a serving architecture such as the Evolved Packet System (EPS) in LTE. In the LTE architecture, EPS is a part of EPC. The Serving Gateway 282 contains functions for eg switching the user plane to support mobility of user equipment, terminating user plane data packets for paging reasons and routing and forwarding data packets. Serving Gateway 282 may be connected to an external MME or both may be physically configured.

Signaling during the handover procedure may take place on the Radio Resource Control (RRC) layer. However, there is information that can be exchanged on the physical radio interface (PHY) layer or on the medium access control (MAC) layer. Examples of this information exchange include transmission of uplink (UL)/downlink (DL) assignments and synchronization signaling as well as user data.

In Fig. 2, the transfer of user data is illustrated with dotted arrows. The transfer of signaling data is illustrated using solid arrows.

According to the embodiment illustrated in Fig. 2, the relay node handover starts with a first step S1, in which the source base station 210 configures the relay node measurement procedure through an RRC reconfiguration message. Simultaneously user data is transferred (a) between relay node 240 and source base station 210 and (b) between source base station 210 and serving gateway 282 . Further, an uplink assignment message is transmitted from the source base station 210 to the relay node 240 to allocate uplink radio resources for communication from the relay node 240 to the source base station 210 . Uplink assignment information can be conveyed on the physical radio interface or on the medium access control layer.

In a second step S2, the relay node 240 is triggered to send a "measurement report" according to the rules set by ie system information, measurement configuration and so on. In this "measurement report" to the source base station 210, the relay node 240 contains information on indicating its capability to configure a standby transceiver in addition to the active transceiver. Optionally, when requested by the source base station 210, the relay node capability may be reported from the relay node 240 to the source base station 210 via a "relay node capability transfer" message.

In the next step S3 , the source base station 210 makes a decision to switch the relay node 240 . This decision is based on the "measurement reports" and/or radio resource management (RRM) information mentioned above.

In the next step S4, the source base station 210 sends a “handover request” message to the target base station 220 . Thus, all necessary information to prepare the relay node handover on the target side is handed over to the target base station 220 .

In a next step S5 , admission control is performed by the target base station 220 . This admission control may rely on received E-UTRAN-Radio Access Bearer (E-RAB) Quality of Service (QoS) information in order to increase the likelihood of a successful handover if the necessary radio resources can be granted by the target base station 220 .

In a next step S6, the target base station 220 prepares for handover and sends a "handover request confirmation" message to the source base station 210. Then, the source base station 210 may transmit a downlink assignment message to the relay node 240 on the physical radio interface layer. The downlink assignment message contains information about downlink radio resources from which the relay node 240 can expect to receive information.

In the next step S7, the source base station 210 generates an RRC message to perform handover. This message may be called an "RRC Connection Reconfiguration" message and is sent by the source base station 210 towards the relay node 240, this message may contain mobility control information about the relay node 240 in case the relay node 240's location changes. According to an embodiment described herein, this message also instructs the relay node 240 to keep the currently serving transceiver active for packet data transmission with the source base station 210 (backhaul transmission).

In a next step S8, the relay node 240 continues the packet data transmission with the source base station 210 based on detecting the indication to keep the serving transceiver active. At the same time, the relay node 240 turns on its backup transceiver in order to synchronize to the target base station 220 .

In a next step S9, the relay node 240 performs synchronization to the target base station 220 and accesses the target base station 220 representing the target cell through a random access channel (RACH). Therefore, a spare transceiver is used.

In the next step S10, the target base station responds with a message indicating the allocation of uplink radio resources and a suitable timing advance (TA) value.

In the next step S11 , when the relay node 240 successfully accesses the target base station 220 , the relay node 240 sends an RRC message to the target base station 220 . This message may be referred to as an "RRC Connection Reconfiguration Complete" message, with which the handover of the relay node 240 from the source base station 210 to the target base station 220 is confirmed.

In the next step S12 , the target base station 220 sends a “handover complete” message to the source base station 210 . This triggers data forwarding between the source base station 210 and the target base station 220 . At this point, the source base station 210 may start to transfer the buffered data packets to the target base station 220 .

At the relay node 240, a predetermined time interval T may be defined, which starts after the "RRC connection reconfiguration complete" message is transmitted from the relay node 240 to the target base station 220 (see step S11). If no data packet is delivered to and/or from the source base station 210 by the previous transceiver of the relay node 240 during this time interval, in the next step S13, the relay node 240 will turn off the previous transceiver, e.g. , in order to save energy. At the same time (at step S13 ) the relay node 240 detaches from the source base station 210 and the data packets temporarily buffered in the source base station 210 are delivered to the target base station 220 .

The next steps and procedures are the same as the original relay node switching. Therefore, they will be mentioned only briefly.

Following step S13 , in order to provide efficient data transfer also in the uplink direction of the handover relay node 240 , a sequence number (SN) status transfer message is transmitted from the source base station 210 to the target base station 220 . This message may be used in order to convey important status information obtained when packet transmission at the source is terminated due to relay node 240 detaching from source base station 210 and attaching to target base station 220 .

Thereafter, the data packets cached and buffered by the source base station 210 are forwarded from the source base station 210 to the target base station 220 . Corresponding data packets are received and they are buffered by the target base station 220 . Simultaneously, user data is transferred (a) between relay node 240 and target base station 220 and (b) between target base station 220 and serving gateway 282 .

In the next step S14 , a "routing exchange request" message is transmitted from the target base station 220 to the MME 280 .

In the next step S15 , the MME 280 sends a user plane update request message to the serving gateway 282 . The user plane update message may contain an instruction to switch the downlink path, which is done in the next step S16, where the "End Marker" message is transmitted from the serving gateway 282 to the source base station 210. With the completion of step S16 , the serving gateway 282 ensures that all arriving data packets of the relay node 240 will now be routed to the correct base station, which is the target base station 220 .

Thereafter, user data is transferred from the serving gateway 282 to the target base station 220 according to embodiments described herein. Further, the “end marker” message is transmitted from the source base station 210 to the target base station 220 .

In a next step S17 , the Serving Gateway 282 is triggered to transmit a “User Plane Update Response” message to the MME 280 .

In the next step S18 , this step is executed to respond to the reception of the “User Plane Update Response” message, and the MME 280 sends a “Path Switch Request Acknowledgment” message to the target base station 220 .

In the next step S19 , the target base station 220 sends a “Relay Node Context Release” message to the source base station 210 . Through this information, the source base station 210 knows that it can release the radio resources that have been allocated to the relay node 240 so far. In the next step S20, the source base station 210 releases these radio resources. From then on, the described relay node switching procedure is completed.

3a to 3d illustrate relay node handover performed in a relay-enhanced telecommunications network 300 . The network 300 includes a first base station 310 , a second base station 320 , a relay node 340 and a user equipment 350 . The relay node 340 spans a relay cell 341 in which the user equipment 350 is located. User equipment 350 is served by two-hop wireless communication (base station to relay node and relay node to user equipment).

According to the embodiment described here, the relay node 340 comprises three radio transceivers, a first radio transceiver 342 , a second radio transceiver 344 and a third radio transceiver 348 . For example, as can be seen from Fig. 3a, a first radio transceiver 342 and a second radio transceiver 344 are used for uplink radio communication with one of the base stations 310 and 320, respectively. The third radio transceiver 348 is used for downlink radio communication between the relay node 340 and the user equipment 350 over the access link 351 . Further, relay node 340 includes a controller 345 coupled to each of radio transceivers 342 , 344 and 348 and configured to regulate and/or control the operation of each radio transceiver 342 , 344 , 348 .

The illustrated handover scenario benefits from the duplex transceiver shown for the relay link extending between the relay node 340 and the two base stations 310 and 320 . Depending on the active status of the radio transceivers 342 and 344 , a first relay link 311 may be established between the relay node 340 and the first base station 310 . Correspondingly, the second relay link 321 can be established between the relay node 340 and the second base station 320 .

In a first operating state shown in FIG. 3 a the first radio transceiver 342 is active and radio data is uplinked and/or downlinked via the first relay link 311 . In contrast, the second radio transceiver 344 is passive such that the second relay link 321 is only a potential (inactive) relay link. This means that the relay node 340 is exclusively connected to the base station 310 via the first transceiver 342 .

In the second operating state shown in Fig. 3b, a handover of the relay node 340 from the first base station 310 to the second base station 320 is prepared. Therefore, the first transceiver 342 is still active so that the data communication between the relay node 340 and the first base station 310 can be continued. However, unlike the first operating state of the telecommunications network 300, the second transceiver 344 also becomes active and measures the signal strength of the pilot signal transmitted by the second base station 320, which now represents Candidate target base stations for node handover. Corresponding measurements are reported to the active transceiver. According to an embodiment described here, radio communication via the first relay link is performed at a first radio frequency and radio communication via the second relay link is performed at a second radio frequency different from the first radio frequency.

In a third operating state shown in FIG. 3 c , the second transceiver accesses a second (target) base station 320 . At this time the first transceiver is still active. In particular, in the described embodiment, the relay node 340 receives the handover decision 311a from the first (source) base station 310 using the first transceiver 342 . The relay node 340 keeps the first relay link 311 active for data traffic.

In a fourth operating state shown in FIG. 3 d , the second (target) base station 320 sends a handover successful message 321 a to the relay node 340 . Therefore, the second transceiver 344 is used to receive this message 321a. In response to this message 321a, the following actions are performed:

1. The first (source) base station 310 releases the relay link 311 .

2. The second transceiver 344 becomes the new active transceiver so that the relay node 340 connects with the second base station 320 using the second transceiver 344 .

3. The first transceiver 342 becomes the corresponding new passive backup transceiver.

The described relay node handover situation (which benefits from two transceivers for different relay links) can provide the following advantages in particular: A): The backup transceiver makes it possible to maintain Data transmission in serving cell. In order to effectively realize this advantage, the source base station should be aware of the relay node's capabilities, ie the fact that dual transceivers can be used for different relay links. Further, the relay node should switch on the second (standby) transceiver while keeping the data transmission with the first (active) transceiver going. Further, the first (source) base station should know when the connection to the second (target) base station is established and should deactivate the previously used active transceiver. B): Compared with the known relay node handover situation, there is less data that has to be forwarded from the first (source) base station to the second (target) base station, because the data before the connection with the second (target) base station The transfer still happens.

C): Relay nodes can be continuously scheduled without interruption caused by relay node switching.

D): Synchronization or random access channel (RACH) failure does not affect data transmission in the serving cell. The data is forwarded to the second (target) base station only if the second (target) base station can indeed serve the relay node.

It should be pointed out that the term "comprising" does not exclude other elements or steps and "a" or "an" does not exclude a plurality. Elements described in association with different embodiments may be combined. It should also be noted that reference signs in the claims should not be construed as limiting the scope of the claims.

List of reference signs:

100 telecommunications network

110 The first base station

111 First relay link

120 second base station

121 Second relay link

130 The third base station

131 The third relay link

140 relay nodes

141 relay cell

142 first radio transceiver

143 First Antenna

144 Second radio transceiver

145 second antenna

150 first user equipment

151 First access link

160 second user equipment

161 Second access link

170 third user equipment

171 The third access link

210 First base station

220 second base station

240 relay nodes

280 Mobility Management Entity (MME)

282 service gateway

291 The first stage: the relay node connects with the first base station RRC

292 The second stage: the relay node connects with the first base station and the second base station RRC

293 The third stage: the relay node connects with the second base station RRC

300 telecommunications network

310 First base station

311 The first relay link

311a Handover decision message

320 second base station

321 Second relay link

321a Handover success message

340 relay nodes

341 relay cell

342 First Radio Transceiver

344 Second radio transceiver

345 controller

348 Third Radio Transceiver

350 user devices

351 access link

Claims (13)

1. the via node that is used for radio telecommunication network (100), described via node (140,240,340) comprising:

First transceiver (142,242), it is applicable to and operates in first operator scheme, wherein the backhaul data traffic is via at via node (140,240,340) and first base station (110,210,310) first repeated link (111 that extends between, 311) transmitted, via node (140,240 is represented in described first base station, 340) source access point, and

Second transceiver (144,344), it is applicable to and operates in second operator scheme, wherein at via node (140,240,340) from first base station (110,210,310) switch to and represent via node (140,240, in the preparation of second base station of target access 340) (120,220,320), via in the via node (140,240,340) and second base station (120,220,320) second repeated link (121,321) that extends between is carried out joining procedure.

2. the described via node of claim as formerly, wherein

-the first transceiver (142,342) is applicable to first carrier frequency operation, and

-the second transceiver (144,344) is applicable to second carrier frequency operation,

Wherein said first carrier frequency is different from described second carrier frequency.

3. as arbitrary described via node of claim formerly, wherein

-first direction antenna pattern and first transceiver (142,342) be associated and

-second direction antenna pattern and second transceiver (144,344) are associated,

Wherein said first direction antenna pattern spatially is different with described second direction antenna pattern.

4. the arbitrary described via node of claim 1-3 as formerly further comprises

Common antenna, it is assigned to first transceiver (142,342) and second transceiver (144,344).

5. the arbitrary described via node of claim 1-3 as formerly further comprises

Be assigned to first transceiver (142) first antenna (143) and

Be assigned to second antenna (145) of second transceiver (144),

Wherein said first antenna (143) is different from described second antenna (145).

6. as arbitrary described via node of claim formerly, wherein

Second transceiver (144,344) further is applied to operate in other first operator scheme, and wherein the backhaul data traffic is via at via node (140,240,340) and second base station (120,220,320) second repeated link (121,321) that extends between is transmitted, from first base station (110,210,310) via node (140 was represented in described second base station after the switching of (120,220,320) was finished to second base station, 240,340) other source access point.

7. the described via node of claim as formerly, wherein

First transceiver (142) further is applied to operate in other second operator scheme, wherein at via node (140,240) from second base station (120,220) to representing via node (140, during the further switching of the 3rd base station (130) of other target access 240) is prepared, carry out other joining procedure via the 3rd repeated link (131) that between via node (140,240) and the 3rd base station (130), extends.

8. be used for preparing with first base station (110 of via node (140,240,340) from cellular telecommunication network, 210,310) switch to the method for second base station (120,220,320), wherein said via node (140,240,340) comprise first transceiver (142,342) and second transceiver (144,344), described method comprises:

In first operator scheme to first transceiver (142,342) operation, wherein the backhaul data traffic is via at via node (140,240,340) and first base station (110,210,310) first repeated link (111,311) that extends between is transmitted, via node (140 is represented in described first base station, 240,340) source access point, and

In second operator scheme, second transceiver (144,344) is operated, wherein at via node (140,240,340) from first base station (110,210,310) switch to second base station (120,220 of the target access of representing via node (140,240), 320) in the preparation, via at via node (140,240,340) and second base station (120,220,320) second repeated link (121,321) that extends between is carried out joining procedure.

9. the described method of claim as formerly, wherein the joining procedure of carrying out via second repeated link (121) comprises:

Carry out process of measurement, its and via node (140,240,340) from first base station (110,210,310) to second base station switching decision of (120,220,320) be correlated with.

10. one of claim 8-9 as formerly described method further comprises:

The fact that via node (140,240,340) is disposed first transceiver (142,342) and second transceiver (144,344) is notified to first base station (110,210,310).

11. the arbitrary described method of claim 8-10 as formerly further comprises

Service via node (140,240,340) is continued via first transceiver (142,342) in notice via node (140,240,340) first base station (110,210,310) during the joining procedure of execution and second transceiver (144,344).

12. the arbitrary described method of claim 8-11 as formerly further comprises

(110,210,310) switch to second base station (120,220,320) from first base station with via node (140,240,340),

(120,220,320) are sent to first base station (110,210,310) and show that switching finishes from second base station with handoff completion message, and

(110,210,310) transmit data to second base station (120,220,320) from first base station, and described data have been addressed to via node (140,240,340) and it has been buffered on first base station (110,210,310).

13. the described method of claim as formerly further comprises

Make first transceiver (142,342), first repeated link (111, the 311) inertia about between via node (140,240,340) and first base station (110,210,310), extending at least.

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